The invention relates to a scale and a method of producing a scale which has a base body on which several partial scale elements made of glass are applied, wherein each partial element has a measurement representation. The invention also relates to a position measuring system having a scale including a base body on which several partial scale elements made of glass are applied wherein each partial element has a measurement representation which can be scanned by a scanning unit having a light source and at least one photodetector for the generation of position-dependent scanning signals.
Position measuring systems capable of measuring great lengths are required for measuring machines and machine tools. To make the manufacture of these position measuring systems easier, several short partial elements are produced and these partial elements are connected on a base body to form a scale for the entire measuring length desired.
A position measuring system and a method for producing a scale are described in German Patent Publication DE 28 47 719 A. The partial elements of the scale are rigidly connected with a base body by welding the partial elements to the base body. In addition, it is possible to arrange spot weld connections at the joints between the partial elements. The partial elements of the scale are made of metal.
A similar position measuring system is described in German Patent Publication DE 1 548 875 A. Several partial elements of a scale are welded on a base body. The partial elements of the scale are formed by a thin foil.
Further position measuring systems wherein a graduation is fastened on a base body by welding are known from European Patent Publication EP 0 624 780 A and Japanese Patent Publication JP 8-145609 A.
A position measuring system, on which the present invention is based is described in German Patent Publication DE 38 18 044 A. Several partial elements of a scale made of glass are placed against each other in the measuring direction on a base body and slidingly connected with the base body.
Advantages of the present invention will become apparent upon consideration of the following detailed description of the present preferred embodiments of the invention, together with the accompanying drawings.
It is an object of the invention to provide a cost-effective and accurate scale, as well as a position measuring system for large measuring lengths in particular.
It is a further object of the invention to provide a cost-effective method for producing a scale, in particular for large measuring lengths.
The particular advantages of the invention lie in that relatively inexpensive glass with a high-quality optical and mechanical surface quality can be used as the support of the measurement representation. A scale which is homogeneous over the entire measuring length is obtained by the connection of the partial scale elements according to the invention.